CN116018217A - Immersed environmental sensor incorporating scale control device - Google Patents

Abstract

An immersion environmental sensor is disclosed, comprising a support (2) having on one face: a sensitive region (8) configured to receive a substance of interest; -an anti-fouling device (4) configured to vibrate at least the sensitive area (8); and a detection device (6) for detecting the presence of at least one substance of interest on the sensitive area (8).

Description

Immersed environmental sensor incorporating scale control device

Technical field and background art

The present invention relates to a liquid medium environmental sensor incorporating an anti-scale device.

Environmental sensors in liquid media may be designed to monitor properties of the media, such as pH, density, etc. of the media, or to measure various characteristics, such as turbidity, chemical substances or the presence of some bacterial strains, etc.

The sensors may be used in an industrial environment, for example, the sensors may be submerged in tanks, pipes, or natural environments (such as oceans, rivers, and canals). A large number of submerged environmental sensors are used. These sensors are not only typically implemented on existing structures, such as offshore platforms or vessels, but may also be part of a dedicated marine observation station. These sensors are also used for monitoring potable water delivery systems and for monitoring river water.

Design and simulation of paper "Conception et simulation d' un micro-capteur ondes de love par e elements finis]", halili et al, J3eA, month 1 2015, available inhttp://dx.doi.org/10.1051/j3ea/2015018To obtain, a love wave sensor for detecting gaseous substances in a liquid medium is described. The love wave sensor includes a piezoelectric substrate and two pairs of interdigitated combs, one pair of combs forming a transmitter and the other pair forming a receiver. Between the two pairs of combs, there is provided a region for collecting gaseous substances, which is called "gap". The emitter generates love waves (love waves) by means of the piezoelectric effect. The wave propagates through the gap towards the receiver, the maximum energy being contained in the guiding layer. After some time (delay time), the sound wave reaches the receiver and is converted into an electrical signal. The propagation speed or amplitude varies depending on the substance deposited on the gap. The clearance surface is typically covered with a sensitive layer adapted to specifically bind to a chemical or biological target.

Any surface immersed in a liquid such as seawater or freshwater is subject to deposition and attachment of organisms (possibly bacteria, algae or even molluscs). This phenomenon is known as biofouling. When environmental conditions are met, the attachment of microorganisms to the material and the propagation of microorganisms can result in the formation of a film on the surface of the material. The film formation takes place in several steps and may be particularly rapid, for example within a few minutes.

After only a few days, the measurement quality of the immersed sensor may be affected by the formation of biofouling on its surface. The gap of a love wave sensor will be covered quickly by a biofilm, which will change the propagation of the love wave.

Thus, an anti-fouling solution is needed to achieve consistent data quality and reduce maintenance required to clean biofilms. The anti-fouling system is of chemical or mechanical type. The chemical system comprises applying a coating carrying a biocide on the surface to be protected. The toxicity of the biocide contained in the coating causes the microorganisms to be dislodged and killed. These systems are polluting and, in addition, they release biocides until they are exhausted and become ineffective.

Mechanical type systems use windshield wipers, for example, to remove microorganisms deposited on sensitive surfaces. However, the wipers themselves are also subject to biofouling. Further, it requires some maintenance to remain effective.

Disclosure of Invention

It is therefore an object of the present invention to provide an immersion environment sensor with improved protection against biofouling.

The above object is achieved by an environmental sensor comprising: a support bearing a surface, a portion of which forms a measurement zone; first means for vibrating at least the measuring surface so as to avoid or at least limit the formation of biofouling films; and second means for performing measurement in the measurement region by generating waves.

Measuring includes, for example, measuring chemical or biological substances contained in a liquid in which the sensor is immersed.

By means of the invention, it is possible to prevent the growth of microorganisms on the measurement area or to remove already deposited microorganisms; and the measurement of the substance of interest, for example by wave propagation, is not distorted by the presence of a biofilm.

Waves that can be used for measurement are, for example, love waves or Rayleigh waves (Rayleigh waves).

For example, the measurement region is vibrated in an out-of-plane mode or Lamb wave (Lamb) mode. Advantageously, multiple modes are excited at different frequencies in order to avoid the occurrence of immobilized areas, which will allow biofouling to develop.

In one exemplary embodiment, a single actuator provides both the scale control function and the measurement function, and the control signal energizes the actuator at multiple frequencies.

In an exemplary embodiment, the first device also ensures that the substance to be measured is guided into the measurement region.

In other words, the environmental sensor according to the invention comprises on the same support means for limiting or even avoiding a biofilm and means for measuring a substance of interest in the liquid in which the sensor is immersed. In this way, an optimal measurement support for the measurement can be maintained in a reduced overall space.

One object of the present application is an immersion environmental sensor comprising a support, one face of which comprises: a sensitive region configured to receive a substance of interest; an anti-scale device configured to vibrate at least the sensitive area, the anti-scale device being carried by the support; and a detection device for detecting the presence of at least one substance of interest on the sensitive area, said detection device being carried by the support.

Preferably, the scale control device is configured to vibrate at least the sensitive area in an out-of-plane vibration mode.

Advantageously, the anti-fouling device is configured to vibrate at least the sensitive area in a plate wave mode, e.g. lamb wave mode.

Preferably, the detection means is configured to implement a surface wave.

In one example, the detection device includes a transmitter of a surface propagating wave disposed on one side of the sensitive area and a receiver of a propagating surface wave transmitted by the transmitter disposed on the other side of the sensitive area.

In another example, the detecting means comprises means for generating a standing wave in the sensitive area and for measuring a change in the resonant frequency of the standing wave.

According to an additional feature, the detection device further comprises a graphene sensor on the sensitive area, and/or a sensor of the field effect transistor type sensitive to changes in ion concentration, and/or an electrochemical sensor.

The sensor may comprise means forming both the anti-fouling means and the detection means.

According to an additional feature, the anti-fouling device is configured to confine at least one substance of interest to the sensitive area.

In one advantageous example, the sensitive area comprises a functionalized layer configured to capture at least one substance of interest.

Another object of the present application is an at least partially submersible detection system comprising at least one environmental sensor according to the invention, and a control unit configured to send a first control signal to the anti-fouling device in order to remove microorganisms from and/or prevent microorganisms from growing on the sensitive area, and to send a second control signal to the detection device in order to perform detection of at least one substance of interest.

The control unit may be configured to apply a frequency sweep over a range of frequencies to the anti-fouling device to excite the medium in different lamb wave modes.

In an exemplary embodiment, the control unit is configured to activate the anti-fouling device before each activation of the detection device.

The control unit may be configured to collect signals from the second device.

According to another example, the control unit is configured to activate the anti-fouling device in order to confine at least one substance of interest to the sensitive area.

Another object of the present application is a method for controlling an environmental sensor according to the present application, the method comprising:

-activating the anti-fouling device.

-stopping the anti-fouling device.

-activating the detection means.

-stopping the detection means.

The anti-fouling device may be activated before each activation of the measuring device.

The control method may provide for activating the scale control device to confine at least one substance of interest to the sensitive area.

For example, the control method applies a frequency sweep over a range of frequencies to the scale control device to excite the medium in different lamb wave modes.

Drawings

The invention will be better understood based on the following description and the accompanying drawings, in which:

FIG. 1 is a schematic representation of an example of an environmental sensor in which a detection device implements a propagating wave.

Fig. 2A, 2B and 2C are schematic representations of rectangular plates excited at different frequencies in lamb wave mode.

FIG. 3 is a schematic representation of another example of an environmental sensor in which a detection device implements a propagating wave.

FIG. 4 is a schematic representation of an example of an environmental sensor in which a propagating wave detection device includes an interdigitated comb.

FIG. 5 is a schematic representation of another example of an environmental sensor in which a detection device implements a standing wave.

FIG. 6 shows confinement of particles of interest on a rectangular support excited at 100kHz in a lamb wave mode.

Fig. 7 shows the confinement of particles of interest on a disc-shaped support excited at different frequencies in out-of-plane mode.

Fig. 8 is an example of a support provided with anti-fouling means for vibrating the support in several modes.

Fig. 9A is a representation of the support of fig. 8 excited in lamb wave mode.

Fig. 9B is a representation of the support of fig. 8 activated in an out-of-plane mode.

Fig. 10A, 10B, 10C, 10D, 10E and 10F are schematic representations of elements obtained during different steps of an example of a method for manufacturing an environmental sensor according to the invention.

Detailed Description

The present application relates to an environmental sensor with improved protection against biofouling or scaling.

In this application, an "environmental sensor" is intended to mean a sensor designed to detect a substance of interest contained in the liquid (chemical or biological) environment of the immersion sensor.

The substance or target of interest is in the form of particles that will bind to the sensitive area of the sensor. The sensor surface has an adhesion property with respect to the substance of interest.

Biofouling may occur in seawater, lakes, rivers, tributaries, natural and artificial protection areas, fresh water in public water systems. The measurement system is suitable for use in such environments.

The environmental sensor may be immersed in water (seawater, fresh water or other liquid).

In this application, the terms "fouling" and "biofouling" will be considered synonymous.

In this application, the terms "biofilm" and "biofouling" will be considered synonymous.

By "anti-fouling action" is meant preventing the formation of a biofilm and/or removing an already formed biofilm.

The sensors may be of different types. The sensor may be designed to monitor parameters such as dissolved oxygen, turbidity, conductivity, pH, or even fluorescence, presence or concentration of some chemical or biological substance. For example, by directly measuring H bound to the sensitive area ₃ 0 ⁺ Ions to determine pH.

In fig. 1, a schematic representation of an example of an environmental sensor can be seen, the environmental sensor comprising: a support 2 (in the example represented, a rectangular plate), a first device 4 designated as an anti-fouling device, and a second device 6 designated as a detection device.

Preferably, the anti-fouling device 4 is arranged relative to the detection device 6 such that the entire sensitive area is subjected to the action of the anti-fouling device. The scale control device may be positioned on the same side as the detection device or on the opposite side.

The sensor comprises at least one sensitive area 8 carried by one face of the support. The sensitive area 8 is the surface that allows the sensor to collect particles of the substance of interest to be detected.

In the example shown, the sensitive area 8 is in the centre of the support and the anti-fouling means and the detection means surround the sensitive area 8.

In an exemplary embodiment, the sensitive area 8 comprises a sensitive layer (not shown) adapted to detect a substance of interest, which layer is referred to as "biofunctionalization layer". For example, the layer includes biological macromolecules having properties that specifically bind to chemical or biological targets.

The macromolecules may be DNA or RNA strands or proteins with specific recognition functions, such as lectins, enzymes, immunoglobulins. The functionalized layer provides biological receptors on the support surface specific for one or more target substances. These biological receptors have a higher affinity for the target, which is referred to as specific recognition. Particles and/or microorganisms, particularly those causing biofouling other than those desired to be detected, may bind themselves to the functionalized layer non-specifically, primarily via electrostatic interactions. However, the affinity of these non-specific bonds is much lower than the affinity characterizing the specific recognition reaction, e.g., several orders of magnitude lower. The binding rate of these non-specific organisms to the functionalized areas will have the same properties as to the binding of other parts of the support (except the sensitive areas), which binding is far less than the binding of the specific substance for which the functionalization is aimed.

According to one example, the functionalized layer includes single chain variable fragments (scFV), which are fusion proteins that allow specific recognition sites to provide higher affinity for peptides (e.g., AR-GCN 4) having antigens corresponding to the scFV fragments, as described in "A label free immunosensor array using single-chain antibody fragments [ unlabeled immunosensor array using single chain antibody fragments ]", natalija Backmann et al, PNAS, 10 month 11 2005, volume 102, 41, 14587-14592.

According to another example, the functionalized layer comprises polyclonal antibodies PAb against ochratoxin a allowing detection of ochratoxin a (called mycotoxin), as described in "An electrochemical immunosensor for ochratoxin Abased on immobilization of antibodies on diazonium functionalized gold electrode [ electrochemical immunosensor for ochratoxin a based on immobilization of antibodies on diazo functionalized gold electrode ]", abd-Elgawad Radia et al, electrochimica Acta [ electrochemical journal ]54 (2009) 2180-2184.

According to another example, the functionalized layer comprises lectins (proteomes), and in particular canavalin a for detection of e.coli, as described in "Detection of Escherichia coli with a label-free impedimetric biosensorbased on lectin functionalised mixed self-assembled monolayer [ label-free impedance biosensor based on lectin functionalized hybrid self-assembled monolayers to detect e.coli ]", haiying Yanga et al, sensors and Actuators [ sensor and actuator ]8 229 (2016) 297-304.

The scale preventing device accelerates and releases the attached microorganisms by vibrating the substrate.

The support 2 has a thickness small enough to exhibit significant vibrations. The thickness of the support 2 depends on the support material and the support mechanical properties. For example, for a polymer or glass support, the thickness of the support may be a few millimeters, or even tens of millimeters. In the case of a silicon support, its thickness is advantageously less than one or a few millimeters.

In the example shown, the anti-fouling device comprises two electromechanical actuators 10 in the form of strips, which are arranged on the face of the support 2 bearing the sensitive area and each extend along the edge of the support 2. Preferably, the actuator 10 is a piezoelectric or ferroelectric actuator, for example made of PZT, AIN or ZnO. Embodiments of piezoelectric or ferroelectric actuators allow for proper incorporation of the system and ensure proper coupling between the actuator and the support. Each actuator 10 comprises an electrode and a piezoelectric or ferroelectric material element arranged between and in electrical contact with the two electrodes.

Alternatively, the electromechanical actuator may be a magnetic actuator, an electrically activated actuator, or a shape memory actuator.

Alternatively, each actuator is replaced by a plurality of actuators arranged parallel to one edge of the support.

Alternatively, the actuator 10 is constrained on the opposite face to the face of the support carrying the sensitive area 8.

The anti-fouling device 4 and the detection device 6 are connected to a power supply and control unit UC. The environmental sensor, the control unit and the power supply are combined to form a detection system.

The electrodes of the actuator 10 are connected to an AC voltage source controlled by a control unit UC. Applying a potential difference between the electrodes generates an electric field in an out-of-plane direction (i.e., the normal direction of the plate). The electric field deforms the piezoelectric material in an out-of-plane direction and in the plane of the plate by the opposing piezoelectric effect. The in-plane deformation produces a mechanical torque that deforms the plate by the bimetal effect. The plate is vibrated by applying an AC voltage. Preferably, the actuators are dimensioned and arranged on the support 2 so as to generate a vibration pattern of the plate that ensures that the anti-fouling action is performed.

For example, the actuator 10 excites the support 2 in its first out-of-plane vibration mode, or in a plate wave mode, such as a lamb wave mode.

In fig. 2A to 2C, it can be seen that the support is shown excited in lamb wave mode at three different frequencies, along with antinodes V and nodes N. The actuator 10 is in the form of a strip and parallel to the antinodes and nodes. For a 30mm by 20mm plate. In fig. 2A, the excitation frequency is 175.4kHz, in fig. 2B, the excitation frequency is 64kHz, and in fig. 2C, the excitation frequency is 132kHz.

Preferably, the frequency of the supply voltage to the actuator 10 is selected such that the plate vibrates at the resonant frequency of the first out-of-plane vibration mode or lamb wave mode, thereby maximizing vibration of the plate. Transducers in which the plate does not vibrate at its resonant frequency do not depart from the scope of the invention.

Because the lamb wave mode is a standing wave mode, it is advantageous to provide a plate excited at different frequencies in the lamb wave mode, with antinodes and nodes at different positions, in order to achieve a uniform anti-fouling action on the plate.

In this example, the detection means implement surface waves (such as love waves or rayleigh waves) which are launched in the sensitive area 8 and whose characteristics depend on the state of the sensitive area.

In the example represented in fig. 1, the detection means comprise a transmitter 12 for generating a propagating wave on one side of the sensitive area and a receiver 14 for receiving the wave on the other side of the sensitive wave.

The transmitter 12 receives an electrical pulse or sinusoidal signal from the control unit UC and generates a surface wave (e.g. a love wave) in the sensitive area. The receiver 14 converts the waves into electrical signals and is collected by the control unit UC. The presence of target particles on the sensitive layer in the acoustic path can produce a mass effect of the interfering waves. By measuring these disturbances, the target particles can be detected and the concentration of the target particles can be inferred as a function of the mass effect percentage.

For example, the sensitive area 8 comprises a base made of a piezoelectric material, wherein the surface waves are generated by the piezoelectric effect. Alternatively, the wave propagates directly in the substrate.

Preferably, as represented in fig. 4, the transmitter 12 and the receiver 14 each have, for example, a pair of interdigitated combs.

In another example, the transmitter and receiver are in the form of a piezoelectric strip and their impedance is measured. The measurement provides a resonant frequency of the system and/or a resonant quality factor of the system. By varying these amounts, particles adhering to the region of interest can be determined. For example, the quality factor is measured by measuring the full width at half maximum (FWHM), quality factor q=resonant frequency/FWHM. Therefore, after the resonance curve is acquired, not only the resonance frequency but also the quality factor can be obtained. The quality factor is also a measure of the energy dissipated by the resonator during each vibration cycle. If a layer of (e.g. biological) material is bonded to the resonator surface, this layer will increase the energy dissipated by the resonator during each vibration cycle, thereby reducing the quality factor.

In another example, the sensor includes piezoresistors on the substrate surface that generate periodic electrical signals synchronized with the generated waves.

In fig. 3, another embodiment can be seen, wherein the anti-fouling means and the detection means are formed by the same actuator. Each actuator is for example rectangular, or a series of squares or rectangles, by means of which not only the support can be actuated, but also measurements can be made, for example by monitoring the impedance as described above.

In the example represented, two actuators are arranged on both sides of the sensitive area and the control unit sends signals at different frequencies to achieve the anti-fouling action and the detection action. For example, the actuators are actuated at a lower frequency for anti-fouling action, and one of the actuators is excited at a higher frequency to generate a propagating wave in the sensitive area. Alternatively, the pair of interdigitated combs forms both the scale prevention means and the detection means.

In another example represented in fig. 5, the detection means 6' operates in resonator mode, i.e. the detection means generates a standing wave in the sensitive area 8 and measures the change in resonance frequency.

In this example, the sensor comprises an actuator forming an anti-fouling device 4 similar to the anti-fouling device in fig. 1, and a detection device 6' comprising a pair of interdigitated combs 15 arranged in vertical alignment with the sensitive area 8, which generates a standing surface wave at the sensitive area 8 and also measures the change in the resonant frequency of the emitted wave. Alternatively, quality factor monitoring may also be performed in addition to or instead of resonance frequency monitoring. Figure of merit monitoring has the additional advantage of providing a means to obtain other characteristics of the detected particle such as Young's modulus or its hydration level.

In the described example, the shape of the support and the sensitive area is rectangular, but it will be appreciated that any other shape of support and/or sensitive area does not depart from the scope of the invention. For example, the support may be disk-shaped and define a disk-shaped sensitive area using a disk-shaped, ring-shaped or arc-shaped actuator.

An example of the operation of the environmental sensor in fig. 1 will now be described.

Submerging the environmental sensor and closing the scale control device 4 and the detection device 6. The support 2 is stationary.

And controlling the descaling stage. The control unit UC preferably applies an electrical signal (e.g. an alternating electrical signal) to the actuator at the resonance frequency of the sought mode (e.g. lamb wave mode). Alternatively, frequency sweeps over a frequency range involving different desired modes are applied to achieve uniform descaling of the sensitive areas. The substrate is then vibrated to create an acceleration effect on the microorganisms on the sensitive area to dislodge them and prevent their growth. The anti-fouling device may be actuated for preventive or remedial action.

The anti-fouling device is activated discontinuously (e.g. periodically). As an example, the anti-fouling device may be activated once an hour or once a day. The frequency of activation, duration of activation, and amplitude and/or frequency of vibration are selected based on the ability of the liquid to form a biofilm and/or the ability of the sensitive surface to be covered with microorganisms. The anti-fouling device may be activated only during the measurement period, before the measurement phase, or periodically at a higher frequency than the measurement phase.

It should be noted that the sedimentation of the particles of interest on the sensitive area 8 is faster than the formation of a biofouling film on this area.

Then, the control unit UC stops the anti-fouling device and starts the detection phase. In particular, the scale control device is stopped during the measurement phase so as not to disturb the measurement, in particular so as not to dislodge particles of interest during the measurement.

The control unit UC then starts the measurement phase and sends a signal to the detection means to generate a surface wave in the sensitive area. Before this, a sedimentation stage may be provided to allow the substance of interest suspended in the liquid to settle on the sensitive area 8. The sedimentation may be passive, the sensor is in a dormant state, or as will be described below, the sedimentation may be active, the actuator of the anti-fouling device being controlled to guide the sedimentation.

The control unit sends an electrical signal to a transmitter 12 which generates a propagation wave P, such as a love wave or a rayleigh wave. The wave propagates in the sensitive area 8 towards the receiver 14, which wave is influenced by the environment, i.e. by the presence or absence of chemicals or bacteria to be detected on the sensitive area 8. The receiver 14 reads the signal resulting from the arrival of the generated environmentally affected waves so that the quality of the biological target that has engaged the sensor sensitive area during the time of sedimentation and measurement can be characterized.

The duration of the measurement is less than the time required to form a biofilm that may distort the detection of the particles of interest. For example, the measurement phase lasts about fifteen minutes, while the time required for the formation of a biofouling film that may interfere with the measurement will be a few hours or tens of hours … …

In the example of fig. 5, the generated wave is a standing wave, which is excited for the whole measurement duration and the frequency of which is measured. When binding biological substances to the sensitive area, the resonance frequency will change (typically due to this additional binding mass) which constitutes a useful detection signal.

The control unit stops the detection device. These detection means may be activated periodically. As an example, these detection means may be activated once an hour or once a day to monitor the quality of the liquid in which the sensor is immersed.

The scale control device may be activated at the end of the measurement to dislodge cells of interest, or at the next biofilm removal stage.

In another exemplary embodiment, the detection of chemical or biological targets in the liquid medium may be achieved by another type of biosensor attached to the support in the sensitive area 8. For example, a graphene sensor may be used; which is capable of detecting the binding of biological substances via their charge. For example, graphene is on a sensitive area.

Alternatively, it is conceivable to implement a plurality of different types of sensors, for example, surface wave sensors and graphene sensors, each occupying a portion of the sensitive area, and/or to implement an ion-selective field effect transistor (ISFET) type sensor, as described in the document "A Scalable ISFET Sensing and Memory Array With Sensor Auto-Calibration for On-Chip Real-Time DNA Detection [ scalable ISFET sensing and memory array with sensor auto-calibration for on-Chip Real-time DNA detection ]", nicolas Moser et al IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS [ IEEE biomedical circuit and systems assembly ], volume 12, 2 nd, month 2018, 4 nd, and/or to implement an electrochemical sensor, as described in the document "Aptamer-Based Electrochemical Biosensor for Interferon Gamma Detection [ Aptamer-based electrochemical biosensor for interferon gamma detection ]", yilu et al, anal. Chem [ analytical chemistry ],2010, 82, 8131-8136.

The sensor also makes it possible to measure the density and/or viscosity of the liquid by measuring the resonant frequency and the quality factor of the vibrating plate interacting with the liquid medium, in particular when lamb waves are implemented. The vibrating plate itself forms the sensitive area. The equation allows the density/viscosity to be determined from the vibration measurements. This determination is described, for example, in the document Neff et al, "Piezoelectric Actuated Glass Plate for Liquid Density and Viscosity Measurement [ piezoelectric actuated glass plate for liquid density and viscosity measurement ]", micromachines Journal [ journal of micromechanics ],11, 248, doi:10.3390/mi 11040348.

In one mode of operation of the sensor, it may be provided that substances in the liquid may be guided so as to limit the attachment of these substances to the sensitive area. For example, depending on the mode of the vibrating structure, the cell of interest is directed to the antinode of the vibration, i.e. the area of the plate with the highest amplitude. This limitation may be in the form of a strip as represented in fig. 6 on a 40mm x 30mm glass plate that is excited in lamb wave mode at a frequency on the order of 100kHz, and any other form on a disc-shaped film with a radius of 800 μm as represented in the image of fig. 7, the film being excited in a first out-of-plane mode with an excitation frequency indicated alongside each image.

In a mode of confining a substance of interest, the control unit UC is configured to activate the actuator in order to vibrate the medium 4 in a standing wave mode, the wavelength λ of which is larger than the size of the cell of interest.

As described above, a plate actuated in a standing wave mode such as a lamb wave mode will deform and have a region of maximum amplitude motion (referred to as an "antinode") and a fixed region (referred to as a "node"). The nodes remain in the plane of the plate, which contains the plate when at rest.

The wavelength of the deformation is designated λ and covers the antinode and the trough. In the mode of operation in which the substance of interest is confined, the standing wave wavelength of the plate deformation is 3 to 20 times the cell size, preferably 10 times the cell size. Preferably, the width of the actuator is substantially equal to the antinode size.

The amplitude of the resonant mode is sufficient to move the liquid and thus the cells suspended in the liquid. Typically, the amplitude is from tens of nanometers to a few microns.

Finite element analysis software (such as

Or->

) The position of the actuator and its size are determined from the deformations in the selected vibration mode. The resonant frequency and amplitude of the mode may also be determined by finite element simulation and/or analytical calculations. The frequency and amplitude are a function of the voltage applied to the actuator.

The determination of the actuator may be made as explained in Casset et al, document "Low voltage actuated plate for haptic applications with PZT thin-film [ low pressure actuation plate for haptic applications using PZT thin films ]", proceedings of Transducers [ transducer theory ] 2013.

Activation of the actuator occurs during sedimentation and before the cells adhere to the receiving surface. The actuator may be activated prior to injection into the cell.

The C-cells are then distributed on top of the accommodation surface 8, and more specifically on top of the vibration antinode of the sensitive surface 8, and move away from the vibration node. The substance settles and adheres to the sensitive surface 8. Alternatively, the actuator may be activated until all the material has settled, or the actuator may be turned off upon settling.

The arrangement of the actuators in fig. 1 allows the cells to be confined to a line along the antinode.

Other restraining operations are also possible by changing the shape and distribution of the actuators. For example, cells are constrained to a checkerboard pattern by distributing actuators in a grid and selecting actuation of the checkerboard pattern.

It is envisaged that different cells are restricted in sequence in different modes by changing the actuation pattern of the plates. For example, cells are sequentially injected into a fluid chamber, each injection changing the actuation pattern. Since cell migration is not a transient phenomenon, it is possible to proceed with the deposition of restricted cells in turn.

The possibility of such particle confinement is also described in G.Vuillermet et al, vuillermet et al, "Inverse Chladni patterns in liquids at microscale [ reverse Cranib mode in liquid on a microscopic scale ]", physical Review Letters [ physical comment flash report ]116 (18), month 5 of 2016.

As an example, an example of determining the size of the actuator 10 of the scale preventing device will be described.

Depending on the organism under consideration, the adhesion of the organism to the sensitive area is variable. The adhesion of the adherent cells between 1nN and 500nN is considered. By estimating eukaryotic cells of mass 1ng, the magnitude of the vibration frequency required for a vibrating plate can be estimated according to the following equation:

in the case of vibration amplitudes delta-1 μm this gives the minimum frequencies involved in the order of 1kHz to 10 kHz. The supports in fig. 2A to 2C show the simulation frequencies in this range.

The actuator in the lamb wave mode of operation is dimensioned, for example, as described in the document Casset et al, "Low voltage actuated plate for haptic applications with PZT thin-film [ low pressure actuation plate for haptic applications using PZT thin films ]", proceedings of Transducers [ transducer theory ]2013, prl 116, 18501 (2016), pages 1-5.

This actuator configuration makes it possible to have a vibration amplitude so that there is a uniform force mapping on the surface. The actuator will be positioned in a manner that facilitates the mode or modes sought.

For example, two 1500 μm wide actuator posts positioned 2200 μm from the plate end provided the desired deformation amplitude at the indicated frequency of 175 kHz. 2000 μm wide actuators, the first actuator positioned 4250 μm from the plate end and the second actuator positioned 17350 μm from the first actuator, provided a pattern with a frequency of 64 kHz.

Implementing multiple actuators allows for greater vibration amplitudes. However, it is conceivable to use a single actuator for the anti-fouling device.

Without limitation, the actuator may be positioned near the outer edge(s) of the support or be constrained to two consecutive anti-nodes of vibration.

Additionally, to excite the medium in multiple modes, a single actuator may be used, or multiple sets of actuators may be used, each set of actuators generating one or more modes. For example, in fig. 8, the anti-fouling device comprises a pair of first actuators 16 in the form of strips extending on both sides of the sensitive area and parallel to two opposite edges, and a second actuator 18 in the form of a ring surrounding the sensitive area 8. The first actuator may excite the sensitive region in a lamb wave mode (fig. 9A) and the second actuator may excite the sensitive region in a first out-of-plane mode (fig. 9B). It should be noted that the second actuator allows to limit out-of-plane deformations within the area surrounded by the second actuator.

Alternatively, the anti-fouling device and the detection device are carried by opposite sides of the support.

The invention allows the sensor to have a larger size, which is defined by the size of the support. Thus, a large amount of liquid can be analyzed.

An example of a method for manufacturing the environmental sensor shown in fig. 1 will now be described.

A piezoelectric stack is formed on a substrate 100, e.g., a semiconductor such as silicon or glass, and includes, e.g., an AIN layer 104 between two Mo layers 102 and 106. The stack is formed, for example, by full plate deposition using sputtering techniques. For example, AIN layer has a thickness of 2 μm, while Mo layer has a thickness of 200nm.

The element thus formed is shown in fig. 10A.

In a next step, the layer 106 is structured, for example by etching, to form the electrodes 110 of the actuator 10 of the anti-fouling device 4, and the interdigitated electrodes of the emitter 12 and the receiver 14 of the detection device 6. For this purpose, a chemical etching step or a plasma etching step may be used.

The element so formed is shown in fig. 10B.

In a next step the AIN layer 104 is structured in order to separate the piezoelectric element 112 of the anti-fouling device from the piezoelectric layer 114 forming the base of the sensitive area 8. For example, the etch layer 104 is etched, such as by chemical etching.

The element so formed is shown in fig. 10C.

In a next step, the layer 102 is structured (e.g. etched) in order to form the electrodes 116 of the anti-fouling device. Layer 116 is present below the detection device but does not act as an electrode.

The element so formed is shown in fig. 10D.

In a next step, a passivation layer 118 is formed over the entire element of fig. 10D in order to isolate the actuator from the external environment. The passivation material being, for example, siO ₂ . The passivation layer 118 has a thickness of 300nm, for example. The passivation layer 118 is opened, for example by etching, in line with the electrodes to allow subsequent electrical connection of the electrodes. In this example, the passivation layer 118 over the sensitive area has been etched. Alternatively, the passivation layer 118 on the sensitive area may remain.

The element so formed is shown in fig. 10E.

In a next step, the connection lines and pads 120 are fabricated at the open portions of the passivation layer, for example by depositing and etching a gold layer. The thickness of the gold layer is, for example, 500nm.

The element so formed is shown in fig. 10F.

Preferably, a plurality of sensors are fabricated simultaneously on the same substrate, and then individualized, for example by dicing or the like.

Claims (18)

1. An immersion environmental sensor comprising a support (2), one face of the support comprising: -a sensitive area (8) configured to receive at least one substance of interest; -an anti-fouling device (4) configured to vibrate at least the sensitive area (8), the anti-fouling device (4) being carried by the support (2); and detection means (6, 6 ') for detecting the presence of at least one substance of interest on the sensitive area (8), the detection means (6, 6') being carried by the support (4), wherein the anti-fouling means are configured to confine the at least one substance of interest on the sensitive area (8).

2. Sensor according to claim 1, wherein the anti-fouling device (4) is configured to vibrate at least the sensitive area (8) in an out-of-plane vibration mode.

3. Sensor according to claim 1 or 2, wherein the anti-fouling device (4) is configured to vibrate at least the sensitive area (8) in a plate wave mode, e.g. lamb wave mode.

4. A sensor according to one of claims 1 to 3, wherein the detection means (6) is configured to implement a surface wave.

5. The sensor according to claim 4, wherein the detection means (6) comprise an emitter (12) of a surface-propagating wave arranged on one side of the sensitive area (8) and a receiver (14) of a surface-propagating wave emitted by the emitter (12) arranged on the other side of the sensitive area (8).

6. A sensor according to claim 4, wherein the detection means (6') comprises means for generating a standing wave in the sensitive area and for measuring a change in the resonant frequency of the standing wave.

7. The sensor of any one of claims 1 to 6, wherein the detection means further comprises a graphene sensor, and/or an ion-selective field effect transistor type sensor, and/or an electrochemical sensor on the sensitive area.

8. A sensor according to any one of the preceding claims, comprising means forming both the anti-fouling means and the detection means.

9. The sensor of any one of the preceding claims, wherein the scale control device comprises an actuator configured to vibrate the medium in a standing wave mode to ensure that at least one species of interest is confined, the wavelength λ of the standing wave mode being 3 to 20 times a given size of the species of interest.

10. The sensor according to any of the preceding claims, wherein the sensitive region (8) comprises a functionalized layer configured to capture the at least one substance of interest.

11. An at least partially submersible detection system comprising at least one environmental sensor according to one of the preceding claims, and a control Unit (UC) configured to send a first control signal to the anti-fouling device (4) in order to remove microorganisms from the sensitive area (8) and/or to prevent microorganisms from propagating on the sensitive area, and to send a second control signal to the detection device (6) in order to perform detection of the at least one substance of interest.

12. A detection system according to the preceding claim in combination with claim 3, wherein the Control Unit (CU) is configured to apply a frequency sweep to the anti-fouling device within a range of frequencies, thereby exciting the medium (2) in different lamb wave modes.

13. The detection system according to claim 11 or 12, wherein the control Unit (UC) is configured to activate the anti-fouling device (4) before each activation of the detection device.

14. The detection system according to one of claims 11 to 13 in combination with claim 5, wherein the control unit is configured to collect signals emitted from the second device.

15. Detection system according to one of claims 11 to 14 in combination with claim 9, wherein the control unit is configured to activate the anti-fouling device (4) in order to confine the at least one substance of interest on the sensitive area.

16. A method for controlling an environmental sensor according to one of claims 1 to 10, the method comprising:

activating the anti-fouling device in an anti-fouling mode,

-stopping the anti-fouling device,

activating the scale control means to confine at least one substance of interest in the sensitive area,

-stopping the anti-fouling device,

-activating the said detection means so as to activate,

-stopping the detection means.

17. The control method of claim 16, wherein the scale control device is activated in a scale control mode prior to each activation of the measurement device.

18. A control method according to claim 16 or 17 in combination with claim 5, comprising applying a frequency sweep over a range of frequencies to the anti-fouling device, thereby exciting the medium (2) in different lamb wave modes.

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